Re: How can I heat food (a sausage) using only solar energy

Hi Marc, 
	Thanks for the interesting question. I hope that what I propose 
will work, but I am not sure it will since I have not tried it. Please let 
me know either way. It will be my first collaboration with a Russian 
scientist. Perhaps we can market it as a new solar powered camp stove if it 
does. 

	Our problem as I see it is that we want to capture light energy 
from the sun and convert it into thermal energy (heat) of the sausage. 
There are two aspects of the problem: 1) directing the energy to the 
sausage and  2) keeping the energy from getting away from the sausage. I 
will tackle #2 first. 

	When sunlight is absorbed by something, like our sausage, or by car 
seats in the summer time, it is converted into thermal energy (heat). 
Thermal energy is really a description of how fast the molecules of 
something are moving and how hard they are bumping into each other. Objects 
that are at a higher temperature than their surroundings try to get rid of 
some of their heat until they drop to the temperature of their 
surroundings. There are a couple of ways of doing this. One is by direct 
transfer. This happens when the molecules of an object that are moving 
really fast bump into the molecules of another object that aren't moving as 
fast. This is what happens when you hold something that is hot and as you 
hold it you notice that it cools off while your hand gets warmer. Another 
way objects cool off is by shedding some of their heat as infrared light. 
This light is similar to the light that we use to see, but a little 
different. When you hold your hand next to something that is hot without 
touching it and feel the heat of it, this is infrared light that is coming 
from the object and transferring some of its heat to your skin. We need to 
come up with a way to keep the sausage from getting rid of the heat we are 
going to give it. For this we need insulation. One of the best insulating 
materials in the world is styrofoam. It is so good that we even used it in 
some experiments in chemistry class a couple times when we wanted to keep 
something from losing heat. 

But we also want something that will allow us to get the heat energy in, in 
the first place. Since we are using light to put the energy in, styrofoam 
by itself wouldn't work, because it isn't transparent. But glass is. And 
glass is excellent at letting visible light through, but at the same time 
blocking infrared light. This is why cars get so hot in the summer 
when the windows are left up on a sunny day. The light goes right through 
the glass, hits the seats of the car and is absorbed as thermal energy. 
Then, when the car seats try to get rid of this thermal energy as infrared 
radiation, the glass keeps it from getting out of the car. 

	So what I propose is that we put the sausage inside a glass jar, 
and then cover most of the jar with some kind of styrofoam, leaving a small 
area for us to let light get into it. You could get the styrofoam from 
coffee cups or something similar. The glass will let light through our 
opening, and block infrared light trying to get back out, and the styrofoam 
will keep the thermal energy of the glass from being lost to the ground and 
air surrounding it. 

	Now, we just need a way to get some light into it. I'm afraid that 
even with our styrofoam covered jar, we still will have a hard time getting 
light energy in faster that our system will lose heat. So what we need is a 
way to get more light in than would normally go in through our opening. A 
magnifying lens would be perfect. That way you could focus light in through 
our opening. I know this might be hard to come by. Even a lens from a pair 
of glasses might work if you could find someone willing to let you use 
theirs. 

	If you can't find something to use as a lens, then we can try plan 
b: mirrors. They don't need to be real mirrors, just something reflective. 
Shiny metal or foil might work. Whatever you use, you won't be able to use 
the styrofoam covering on the jar; we'll need the extra space to let the 
light in. You'll also need to put the mirrors around the glass jar and 
shape them so that they reflect as much of their light as possible into it. 
It also might help if you put something black inside the jar to focus the 
light onto. Black objects absorb more light than objects of any other 
color. 

Good luck and let me know how it turns out.

Sincerely,
Todd Holland
Graduate student in biophysics and certifiably Mad Scientist.